Just how much shear will there be?

[ALhurricane]

There have been constant talks on just how much shear Ivan will encounter during his trek through the Gulf of Mexico. Miles Lawrence is going with the SHIPS model all the way it looks like. Well, I have done some looking here this morning and I am not so confident there will be as much shear as Lawrence is talking about.

First let's take a look at the 24-hour shear tendency map from the Univ. of Wisconsin-Madison..

http://cimss.ssec.wisc.edu/tropic/real- ... g8sht.html

You'll see that there is indeed increasing shear over the northern Gulf. That is associated with the passing shortwave. There is not much shear a all directly to the north of Ivan and is in fact entering an area of decreasing shear.

Taking a look at some model fields... we see the 06z GFS initialized this pattern fairly well. Here are the 250 mb winds...

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_000m.gif

Now let's take a look out to 48 and 72 hours...

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_048m.gif

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_072m.gif


While there is indeed some westerly shear... the overall pattern is for an overall ridging pattern over the hurricane. This combined with the fact that Ivan looks to now traverse the warmer waters of the east central or central Gulf lead me to believe that while there will be some weakening due to some westerly shear, I have my doubts it will be enough to weaken it significantly. I still look for this to be a low end 4/high end 3 at landfall.

[Brent]

Just watched a video update on the internet from my local met up here. He doesn't see the shear either. He was stressing about the no skill in intensity forecasting. He said people need to prepare for a Cat 4 landfall along the MS/AL and Western Florida Panhandle coastline.

[skysummit]

Plus, if Ivan can withhold it's CAT 4 or 5 status upon entering the GOM, as large as Ivan is, it may just create its own environmnet and literally "Push" the shear away.

[dennis1x1]

according to this....lots...


http://www.nhc.noaa.gov/ftp/graphics/AT ... 30253I.gif


notice that the official forecast of 105kts at landfall still much higher than probability..

[Dean4Storms]

Agree, with the Shortwave lifting out the shear will only lessen. On top of that Ivan is so large and has an impressive outflow and the pattern around him so weak that his ridge aloft may help him. I just don't see that much shear either, nothing over 20kts.

[Hurricane Cheese]

Shear is a fickle thing...just look at Frances.

This is the biggest uncertainity with Ivan right now, more so than the track even IMO because there is a large difference between a Cat 4 and a Cat 2/3 as we all know.

I must say, I see some shear, but not as much as being forecasted, and the CISMISS data from Bucky Badger certainly illustrates that.


It will be an interesting 3 days to say the least....